1. Field of the Invention
The present invention relates to a vehicle steering system.
2. Description of Related Art
An electric power steering system (EPS) has been widely used, in which a steering assist force is given to a driver's steering effort with the use of an electric motor or the like. In recent years, an electric power steering system has been used in an electrically driven vehicle such as an electric vehicle or a hybrid vehicle, the electrically driven vehicle being provided with an electric storage device such as a secondary battery or a capacitor, and traveling with the use of a drive force generated using electric power stored in the electric storage device. For example, refer to Japanese Patent Application Publication No. 2008-143483 (JP 2008-143483 A).
In such an electrically driven vehicle, electric power may be directly supplied to the electric power steering system with the use of a high-voltage and large-current battery for traveling that is a large-capacity electric storage device. However, when a hybrid vehicle, in which the above-described electric power steering system is provided, has a collision while traveling, it is necessary to stop the supply of electric power to the electric power steering system in order to avoid a situation in which electric shock occurs due to a high voltage, for example, a situation in which a current flows to a driver via a steering mechanism. However, when driving of vehicle wheels is stopped, it is not possible to continue to perform a steering operation, and it may not be possible to cause the vehicle to travel in a limp home mode to evacuate the vehicle. Electric insulation may be achieved using electric control, but when a failure occurs in a control circuit or the like after the collision occurs, it is not possible to completely protect the driver from electric shock.